The currently available electronic apparatus all have an enhanced performance. However, the electronic elements in the electronic apparatus for signal processing and data computing also produce more heat than before. The most frequently used heat dissipation devices include heat pipes, heat sinks, vapor chambers and the like. These heat dissipation devices are so arranged that they are in direct contact with the heat-producing electronic elements to ensure further enhanced heat dissipation effect and prevent the electronic elements from being burnt out due to overly high temperature thereof.
The vapor chamber is a device that enables heat transfer between two large surfaces to achieve the purpose of quick heat dissipation. Unlike the heat pipe that achieves heat dissipation via point-to-point heat transfer, the vapor chamber is more suitable for use in an electronic device having a relatively small internal space.
Conventionally, the vapor chamber is associated with a base board for use, so that heat produced by the heat-producing elements on the base board is transferred to the vapor chamber for quick dissipation into ambient air. To mount the vapor chamber to the base board according to a conventional way, at least one hole is formed on the vapor chamber at a position not interfering with the hollow portion of the vapor chamber. For example, a through hole is formed at each of four corners of the vapor chamber outside the closed inner space of the vapor chamber, and an internally threaded hollow copper shaft is inserted in each of the through holes. The base board is also provided with fastening holes at positions corresponding to the hollow copper shafts on the vapor chamber. Then, externally threaded fastening elements are correspondingly screwed into the internally threaded hollow copper shafts and the fastening holes to fixedly mount the vapor chamber on the base board. The above conventional mounting manner has a disadvantage. That is, the hollow copper shafts are located at four corners of the vapor chamber that are somewhat distant from the heat-producing element. In this case, the vapor chamber mounted on the base board could not be closely attached to the heat-producing element and thermal resistance tends to occur between the vapor chamber and the heat-producing element. To overcome the above problem, it has been tried to provide the hollow copper shafts on the vapor chamber at positions closer to the heat-producing element. In this case, the hollow copper shafts are directly extended through the closed inner space of the vapor chamber. While the above improved mounting manner can ensure the close attachment of the vapor chamber to the heat-producing element and avoid the occurrence of thermal resistance, the hollow copper shafts penetrating the closed inner space of the vapor chamber would endanger the air-tightness of the vapor chamber, rendering the vapor chamber no longer in a vacuum state. Further, with the hollow copper shafts penetrating the closed inner space of the vapor chamber, it is possible the flow path of the working fluid in the vapor chamber is hindered by the hollow copper shafts to cause lowered heat transfer efficiency. In a worse state, the penetrating hollow copper shafts might cause leakage of the working fluid and accordingly, failure of the vapor chamber in its heat transfer effect.
Please refer to FIGS. 1 and 2. disclose a heat spreader structure 5 including a main body 51 having a first flat plate 511 and a second flat plate 512. The first and the second flat plate 511, 512 are two separate members but connected to each other along peripheral lips 513 formed around them, so that the main body 51 internally defines a sealed chamber 514. Depressions 5111 are formed on the first flat plate 511 at locations far away from the peripheral lips 513 with their flat bottoms in contact with the second flat plate 512. Through holes 52 penetrate some of the depressions 5111 on the first flat plate 511 and penetrate the second flat plate 512. The depressions 5111 penetrated by the through holes 52 respectively have a round wall surface 5112. The round wall surfaces 5112 are correspondingly connected to annular areas 5121 on the second flat plate 512, such that the through holes 52 are isolated from the main body 51. Spacing pillars 53 are extended between and in contact with the first and the second flat plate 511, 512. And, a wick structure 54 is provided in the sealed chamber 514. In the above heat spreader structure 5, while the depressions 5111 can serve as a supporting structure and the connection of the through holes 52 to the annular areas 5121 provides an airtight effect, the depressions 5111 inevitably largely reduce the space in the sealed chamber 514 of the heat spreader structure 5 for gas-liquid circulation. The provision of the depressions 5111 also reduces the contact areas between the heat spreader structure 5 and the heat source, which results in lowered heat transfer efficiency. Further, it is uncertain whether or not the through holes 52 are exactly airtight.
Therefore, the conventional penetration structures for heat dissipation devices have the following disadvantages: (1) having the problem of thermal resistance; (2) reducing the heat transfer areas of the heat dissipation devices; and (3) lowering the heat transfer efficiency of the heat dissipation devices.